Fiberglass reinforced composite materials have been available for use in marine and aerospace materials for some time. Other fiber materials such as carbon and aramid fibers are available for use, although at substantially higher cost. The articles of the present invention may use any known manufacturing method, including compression molding, laminating, spray up, hand laying, prefabricated lay-up (prepreg), compression molding, vacuum bag molding, pressure bag molding, press molding, transfer molding, vacuum assisted resin transfer molding, pultrusion molding, filament winding, casting, autoclave molding, centrifugal casting resin transfer and continuous casting. The properties of the composite are controlled by the fibers and the resin, and synergy between the two, that produces material properties unavailable from the individual materials.
A number of resins are useful in the manufacture of composite articles including polyester resin, vinylester resin and epoxy resin. Polyester resin is suitable for a number of situations. Vinylester resin has lower viscosity precure and more flexible postcure than polyester resin and is typically more resistant to degradation. Epoxy resin is typically transparent when cured. Epoxy resin is a polyether resin formed by the polymerization bisphenol A, bisphenol F, bisphenol C, and compounds of similar structure with epichlorohydrin resulting in the formation of the reactive oxirane linkage. Epoxy resins may react with a variety of curing agents, including amines, anhydrides, mercaptans, polyesters to form an infusable solid. The reaction is a condensation reaction typically does not create by-products. Cured epoxy resins have high strength, and low shrinkage during curing. They are used as coatings, adhesives, castings, composites, or foam. Epoxy resins are also desirable for use in high strength applications as a structural matrix material or as a structural glue. Phenolics are thermosetting resins formed by the condensation of phenol, or of a phenol derivative, with an aldehyde, typically a formaldehyde. Phenolics are used chiefly in the manufacture of paints and plastics. Other specific high strength modulus resins include bismaleimide, poly-amide, vinyl ester phenolic, ethylene-acrylate or methacrylate copolymers, high strength medium modulus thermoplastics such as an ionomer (i.e. crosslinked ethylene-methyl acrylate or methyl methacrylate copolymer), polycarbonate, polyurethane, nylon, aramid, modified epoxies.
The most common high strength glass composition for making continuous glass fiber strands is “S-Glass.” S-Glass is a family of glasses composed primarily of the oxides of magnesium, aluminum, and silicon with a chemical composition that produces glass fibers having a higher mechanical strength than E-Glass fibers. A commonly used member of the S-Glass family is known as S2-Glass. S2-Glass includes approximately 65 weight % SiO2, 25 weight % Al2O3, and 10 weight % MgO. S-glass has a composition that was originally designed to be used in high-strength applications such as ballistic armor.
R-Glass is a family of glasses that are composed primarily of the oxides of silicon, aluminum, magnesium, and calcium with a chemical composition that produces glass fibers with a higher mechanical strength than E-Glass fibers. R-Glass has a composition that contains approximately 58-60 weight % SiO2, 23.5-25.5 weight % Al2O3, 14-17 weight % CaO plus MgO, 0% B2O3, 0% F2 and less than 2 weight % miscellaneous components. R-Glass contains more alumina and silica than E-Glass and requires higher melting and processing temperatures during fiber forming. Typically, the melting and processing temperatures for R-Glass are at least 160° C. higher than those for E-Glass. This increase in processing temperature typically requires the use of a high-cost platinum-lined melter. In addition, the close proximity of the liquidus temperature to the forming temperature in R-Glass requires that the glass be fiberized at a higher temperature than E-Glass.
Other known high-strength glass compositions can be found in U.S. patent application Ser. No. 11/267,739 entitled “Composition for High Performance Glass, High Performance Glass Fibers and Articles Therefrom”, published as U.S. Patent Application Pub. No. 2008/0009403.
Both R-Glass and S-Glass are produced by melting the constituents of the compositions in a platinum-lined melting container. The costs of forming R-Glass and S-Glass fibers are dramatically higher than E-Glass fibers due to the cost of producing the fibers in such melters. Thus, there is a need in the art for methods of forming glass compositions useful in the formation of high performance glass fibers from a direct-melt process in a furnace substantially free of platinum or other noble metal materials and products formed there from.